Dynamo-electric machine



Aug. 17 1926. 1,596,255

' L. J. STEPHENSON DYNAMO ELECTRIC ncanm Fild March 28, 1921 lazy/Z5 ,a ze/zraz Patented Aug. 17, 1926.

UNITED STATES PATENT OFFICE.

LmGH J. STEPHENSON, OF CHICAGO, ILLINOIS, ASSIGNOR TO ."B. V. BECKER, LEIGH J. STEPHENSON, GEORGE B. BURRAGE, WILLIAM '1. BENTON, AND LYNN A. WIL- LIAMS, TRUSTEES, ALL OF CHICAGO, ILLINOIS.

DYNAIO-ELECTRIC MACHIN E.

Application filed larch 28, 1921. Serial No. 468,352.

My invention relates to improvements in dynamo electric machines, and is particularly concerned with the provisions of means for controlling the operation of such '6 machines to cause them to operate either as motors or as generators. My invention is particularly adaptable to dynamo electric machines designed for driving traction vehicles or other machines, the speed of which must be adjusted and for driving machinery which is frequently started and stopped.

My present invention relates to certain modifications of the apparatus described and claimed in my Reissue Patent No.

14,787 of January 6, 1920.

The principal objects of my present invention are 2- F irst-to provide novel means for com- Third-to provide means of the character described which is of simple construction and economical to manufacture.

Other objects will appear as this descrip- 80 tion progresses, reference being had to the accompanying drawings in which Figure 1 is a schematic diagramof the apparatus embodying my invention, and Figure 2 is a simila dlagra-m showing a modified form of my invention.

In the embodiment of my invention illustrated in Figure 1, the reference character 5 indicates the armature of a dynamoelectric machine which is intended to operate as a motor for driving traction vehicles or other machines, the speed of which must be varied and controlled, or for driving ,machinery which is to be frequently started and stopped. Current is supplied to the armature 5 thru the line wires 6 and 7, the

switches and the adjustable starting resis tance (R) I have illustrated this dynamo electric machine as being provided with a commutating-field winding 8.

The field winding 9 of the dynamo electric machine which is preferably of the shuntfield type, is connected in series with the armature- 10 of the regulatin dynamo electric machine which will herea ter be referred to briefly as the regulating dynamo, to form a field winding circuit which is connected directly across the line wires 6 and 7. The armature 10 of the regulating dynamo is illustrated as being mounted upon the shaft 11 of the dynamo electric machine having the armature 5, so that the armature of the regulating dynamo must necessarily operate at a speed constantly proportional to the speed of the dynamo electric machine having the armature 5. The regulating dynamo has a field winding 12 which is connected in parallel with the field winding 9 by means of conductors 13 and 14, there being an adjustable rheostat 15 connected in series with the field winding 12, by means of which the current thru the field winding 12 can be adjusted from zero to maximum. J

The construction thus far described is identical with that described and claimed in my re-issue patent above referred to and further description thereof is, therefore,

unnecessary. My present invention differs from that described in my re-issue patent in that it provides a second field winding 16 for the regulating dynamo, which is differentially wound with respect to the field winding 12 so that during motor 0 eration it opposes the field winding 12 an during the regeneration period it assists the field winding 12. The field winding 16 is connected by means of conductors 17 and 18 across the terminals of the shunt resistance 19, which has a low ohmic resistance, and which is connected in series with'the armature 5, so that the current in the field winding 16 is always constantly proportional to the current thru the armature 5. If desired, the windin '16 can be connected directly in series with t e armature 5, so that it will carry the entire current thru the armature 5.

In operation, when the dynamo electric machine, havin the armature 5, is functioning as a motor, if an additional load should be imposed thereon, as for instance, when a car driven by the apparatus described herein begins to mount a grade, the speed of the motor will decrease, thereby permitting an initial increased current thru the armature and a proportional increase in 'current thru the field winding 16. As field winding 16, during the motoring operation op oses the field winding 12, the excitation o the regulating dynamowill be decreased, thereby permitting an increase of current thru the field winding 9 with a consequent reduction in speed of the dynamo electric machine, having the armature 5. This reduction in speed of the armature 5 causes a corresponding reduction in speed of the armature 10, thereby reducing the counter electromotive' force of the regulating dyname and permitting a still further increase iii current thru the field winding 9 and a further reduction in the speed of the motor. This action con iues until the increased field strength of the dynamo electric machine will produce a torque suificient to carry the increased load.

During the generating action, that is, while the dynamo electric machine is functioning as a generator, to convert the momentum of the load into electric energy, which is returned to the line, field winding 16 assists the field winding 12, as a result of which anything tending to increase the speed of the motor, such, for instance, as the car travelling down grade, tends to increase the counter electromotive force of the re lating dynamo and correspondingl" gl creases the field produced by field winding 9. It will, therefore, be seen that the metion of the winding 16, during regeneration,

is to limit the regenerated current to an extent which is determined by the relative proportions of the two field windings, 12 and 16.

The arrangement shown in Figure 2 is similar to that described above, except that in this figure thefield winding 9' of the dynamo electric machine having the armature 5, is of the series type, and the field winding 12' of the re atin dynamo is connected in series wit the eld winding I these two windings being in turn connected with the armature 10 of the regulating dynamo to form a field winding circuit which may be connected by conductors 20 and 21 with any suitable source of current which may be the source supplying current tothe armature 5 or a separate and distinct source, as, for instance, a motor generator set.

For adjustin the relative amounts of current thru the eld windings 9 and l2',-I connect an adjustable resistance 22 in parallel with the field winding 12. Otherwise, the construction illustrated in this figure is the same as'that shown in Figure 1. This modified form of my apparatus functions in substantially the same manner as that shown in Fi re 1.

In both em diments of my invention, the field winding 16, by its reaction upon the armature 10, and therefore upon the field windings 9 and 9, tends to compensate for fluctuation in line voltage during either the motoring or the generating period. During motoring, any increase in line voltage will tend to cause a greater current thru the field winding 16, thereby decreasing the voltage of the regulating dynamo and correspondingly increasing the current thru the field winding 9. This increase in current thru the field winding 9 will cause a corresponding increase in the counter electromotive force of the dynamo electric ma chine and consequently tend to prevent a surge of current therethru. Conversely, any drop in the line voltage during the regeneration period will cause a corrcspondin increase in the current thru the field winding 16, which will increase the voltage of the regulating dynamo and decrease the current thru the field winding 9, thereby decreasing the generated voltage of the dynamo elecform a field winding circuit, means for impressing a voltage on said field winding circuit, a field Winding for said regulating dynamo connected in parallel with said motor field'winding, a second field winding for said regulating dynamo, differentially wound with respect to said first named regulating dynamo field winding, means for supplying current to said second field winding at a rate constantly proportional to the current thru said motor and means for causing said regulating dynamo to rotate at a speed constantly proportional to the speed of said motor.

2. The combination with a dynamo electric machine having a field winding, of in regulating dynamo connected in series with .said field winding to form a field winding means for supplying a current to said sec- 0nd field win which is constantly proportional to the current thru said dynamo electric machineand means for causi laid regulating dynamo to rotate at a 1 constantly proportional to the speed of said portional to the current thru said dynamo dynamo electric machine. electric machine field winding and the other 10 3. The combination of a dynamo electric of which carries a current proportional to machine, having a field windin and the current thru the armature of said 6 a regulatin dynamo, the armature 0 which dynamo electric machine. is connect in series with said field winding, V In witness whereofQI hereunto subscribe said regulating d namo having two field my name this 22nd da of March, 1921. windings, one of w ich carries a current pro- LEIGH STEPHENSON. 

